Like Tom, confused about measure of distance (9)
I believe the answer is:
kilometre
'measure of distance' is the definition.
(I've seen this before)
'like tom confused about' is the wordplay.
'confused' indicates an anagram.
'about' becomes 're' ('re' means regarding or about).
'like'+'tom'='liketom'
'liketom' anagrammed gives 'kilomet'.
'kilomet'+'re'='KILOMETRE'
(Other definitions for kilometre that I've seen before include "Unit of length" , "Measure of distance" , "Metrical measure of 0.62 miles" , "K stands for this" , "0.621 of a mile" .)